Chris we have a 40 acre puppy pen, .which is about a mile of wire We have two wires top and one on the bottom. We have a 25 mile ac box on the bottom wire and a 20 mile ac box on the top wire. We also have a small holding pen where we wire break our coyotes & get them use to us coming feed them that's about 40' circle or whatever it was that 100' of wire was. we keep a solar panel with a 15 mile dc charger on it. the main thing is keeping the fence hot wire clear of debris and keep it sprayed to keep the grass off. we have not had a problem of yet doing this. it will make you laugh at them jokers scratching at the fence we you first turn them out the holding pen cause they will start scratching about a foot from the fence and in the next few days they start scratching further and further away. I will agree though the higher the joules out put the stronger the wire hits especially if you know you wont be able to keep the fence and wire real clean. I would also like to say if you gonna keep fox in your pen to add a second stran of wire on the bottom. Hope this helps God bless and happy hunting/running!!!! P.S I got them from Tractor Supply!!
Kencove 13 joules about 250$ right in the kencove website and has a switch on bottom to switch to half power when running pups alsi has nice troubleshooting features if you have a short in your wire. With 3 year warranty.